Methods and systems for enabling feedback in wireless communication networks

ABSTRACT

Aspects of the present invention provide additional MAC functionality to support the PHY features of a wireless communication system framework. The additional MAC functionality aids in enabling feedback from wireless terminals to base stations. In some aspects of the invention the feedback is provided on an allocated feedback channel. In other aspects of the invention the feedback is provided by MAC protocol data units (PDU) in a header, mini-header, or subheader. The feedback may be transmitted from the wireless terminal to the base station autonomously by the wireless terminal or in response to an indication from the base station that feedback is requested. Aspects of the invention also provide for allocating feedback resources to form a dedicated feedback channel. One or more of these enhancements is included in a given implementation. Base stations and wireless terminals are also described upon which methods described herein can be implemented.

RELATED APPLICATIONS

This application is the National Stage of International PatentApplication No. PCT/CA2005/000959, filed Jun. 22, 2005. InternationalPatent Application No. PCT/CA2005/000959 claims the benefit of U.S.Provisional Patent Application No. 60/581,356 filed on Jun. 22, 2004,U.S. Provisional patent application No. 60/582,298 filed on Jun. 24,2004, U.S. Provisional patent application No. 60/601,178, filed on Aug.13, 2004, Provisional Patent Application No. 60/614,621, filed on Sep.30, 2004, Provisional patent application No. 60/619,461 filed on Oct.15, 2004 and Provisional patent application No. 60/642,697 filed on Jan.10, 2005, all of which are hereby incorporated by reference in theirentirety.

FIELD OF THE INVENTION

The invention relates to wireless communication systems, in particulardevices and methods for providing feedback from wireless terminals tobase stations.

BACKGROUND OF THE INVENTION

Wireless metropolitan area networks (MAN) are networks implemented overan air interface for fixed, portable, and mobile broadband accesssystems. Some wireless MANs utilize orthogonal frequency divisionmultiplexing (OFDM) for signaling between mobile terminals and basestations. OFDM is a form of multiplexing that distributes data over anumber of carriers that have a very precise spacing in the frequencydomain. The precise spacing of the carriers provides several benefitssuch a high spectral efficiency, resiliency to radio frequencyinterference and lower multi-path distortion. Due to its beneficialproperties and superior performance in multi-path fading wirelesschannels, OFDM has been identified as a useful technique in the area ofhigh data-rate wireless communication, for example wireless metropolitanarea networks (M). Orthogonal frequency division multiple access (OFDMA)is a multiple access technology that utilizes OFDM techniques.

MIMO antenna systems are also being considered for incorporation intowireless MANs. MIMO systems use multiple transmitting and multiplereceiving antennas for communication of information. MIMO antennasystems allow spatial diversity. Spatial diversity that takes advantageof transmitting data from multiple sources that have a known physicalspacing.

Currently there are methodologies for dealing with particular aspects ofwireless MAN, for example OFDM communications. However, thesemethodologies do not deal with ways to incorporate the newer concepts ofMIMO. In addition, both MIMO and non-MIMO wireless MADs are continuingto introduce and support additional functionality that requires numerousadditional types of feedback information to be transmitted from thewireless terminal to the base station. In some cases the feedbackmechanisms of the current methodologies cannot support the transmissionof the additional number of types of feedback information. Furthermore,the current methodologies are limited in the capacity of informationthat they can feedback from the wireless terminal to the base station.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a methodin a wireless terminal for enabling feedback in an uplink transmissionof a communication system from the wireless terminal to a base station,the method comprising: the wireless terminal transmitting feedbackinformation in a MAC feedback protocol data unit (PDU) of a data frame,the feedback information comprising feedback type and feedback content,wherein the wireless terminal transmitting feedback information isperformed subsequent to the wireless terminal autonomously transmittingon a dedicated feedback channel an indication that the wireless terminalhas feedback information to transmit.

According to a second aspect of the invention, there is provided amethod in a wireless terminal for enabling feedback in an uplinktransmission of a communication system from the wireless terminal to abase station, the method comprising: the wireless terminal receiving anindication of a type of feedback information being requested by the basestation in an information element in an uplink resource allocationportion of a data frame; in response to receiving the informationelement, the wireless terminal transmitting feedback information in aMAC feedback protocol data unit (PDU) of the data frame, the feedbackinformation comprising feedback type and feedback content.

According to a third aspect of the invention, there is provided a methodin a wireless terminal for enabling feedback in an uplink transmissionof a communication system from the wireless terminal to a base station,the method comprising: the wireless terminal receiving a pollingindication of a type of feedback information requested by the basestation, the polling indication being an information element in anuplink resource allocation portion of a data frame; in response toreceiving the polling indication, the wireless terminal transmittingfeedback information in a feedback channel of the data frame.

According to a fourth aspect of the invention, there is provided amethod in a base station for enabling feedback in an uplink transmissionof a communication system from a wireless terminal to a base station,the method comprising: the base station transmitting a location in adata frame for allocating requested feedback information to be receivedby the base station, the base station transmitting the location in aninformation element in an uplink resource allocation portion of the dataframe.

According to a fifth aspect of the invention, there is provided a methodin a base station for enabling feedback in an uplink transmission of acommunication system from a wireless terminal to a base station, themethod comprising: the base station transmitting an indication of a typeof feedback, information requested by the base station, the indicationcomprising an information element in an uplink resource allocationportion of a date frame.

According to a sixth aspect of the invention, there is provided a methodfor dynamically allocating at least one feedback channel to a wirelessterminal in a MIMO-OFDM system, the method comprising: a base stationtransmitting to the wireless terminal in a data frame: 1) a uniqueidentifier of feedback channel resources including at least one feedbackchannel assigned to the wireless terminal; 2) a location of the feedbackchannel resources in the data frame; 3) a total number of the at leastone feedback channels included in the feedback channel resourcesassociated with the unique identifier; 4) for each of the at least onefeedback channel of the feedback channel resources associated with theunique identifier, the base station transmitting to the wirelessterminal; i) a feedback type to be transmitted by the wireless terminalto the base station; ii) a feedback channel type to be transmitted bythe wireless terminal to the base station; iii) if the feedback type isa MIMO mode or permutation mode feedback type, a feedback cycle fortransmitting feedback information pertaining to a transmission channelbetween the base station and the wireless terminal.

According to a seventh aspect of the invention, there is provided amethod in a base station for enabling feedback in an uplink transmissionof a closed-loop communication system from at least one wirelessterminal to a base station, the method comprising: transmitting arequest for feedback information and an allocation of uplink resourcescomprising at least one feedback channel in one or more data frames onwhich the at least one wireless terminal is to transmit the requestedfeedback information to the base station; receiving the feedbackinformation in accordance with the request on the at least one allocatedfeedback channel in the one or more data frames, until all the requestedfeedback information is received by the base station.

According to an eighth aspect of the invention, there is provided amethod for enabling feedback in an uplink transmission of a closed-loopcommunication system from a wireless terminal to a base station, themethod comprising: the wireless terminal transmitting a messagecomprising feedback content, the format of the feedback contentdetermined by a format index that is an indication of a respectivetransmission format of the feedback content.

According to a ninth aspect of the invention, there is provided a methodfor enabling feedback in an uplink transmission of a closed-loopcommunication system from a wireless terminal to a base station, themethod comprising: the base station transmitting a request message forfeedback to be received from the wireless terminal, the format of thefeedback determined by a format index that is an indication of aTransmission format of the feedback content.

Other aspects and features of the present invention will become apparentto those ordinarily skilled in the art upon review of the followingdescription of specific embodiments of the invention in conjunction withthe accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described withreference to the attached drawings in which:

FIG. 1 is a block diagram of a cellular communication system;

FIG. 2 is a block diagram of an example base station that might be usedto implement some embodiments of the present invention;

FIG. 3 is a block diagram of an example wireless terminal that might beused to implement some embodiments of the present invention;

FIG. 4 is a block diagram of a logical breakdown of an example OFDMtransmitter architecture that might be used to implement someembodiments of the present invention;

FIG. 5 is a block diagram of a logical breakdown of an example OFDMreceiver architecture that might be used to implement some embodimentsof the present invention;

FIG. 6 is a schematic view of an OFDM frame for use with embodimentsprovided by the invention;

FIG. 7 is a signaling diagram for communication between a base station(BS) and a wireless terminal according to one embodiment of theinvention;

FIG. 8 is a signaling diagram for communication between a BS and awireless terminal according to another embodiment of the invention;

FIG. 9 is a signaling diagram for communication between a BS and awireless terminal according to a further embodiment of the invention;

FIG. 10 is a signaling diagram for communication between a ES and awireless terminal according to still a further embodiment of theinvention;

FIG. 11 is a flow chart for a method of a BS polling a wireless terminalin accordance with an embodiment of the invention;

FIG. 12 is a block diagram of a feedback header in accordance with anembodiment of the invention;

FIG. 13 is a block diagram of a feedback header in accordance withanother embodiment of the invention;

FIG. 14 is a block diagram of a feedback mini-header in accordance withan embodiment of the invention, and

FIG. 15 is a diagram of a pilot pattern used in an OFDM environment;

FIG. 16 is a flow chart for a method of a BS allocating uplink resourcesfor closed-loop MIMO communication between the BS and a wirelessterminal in accordance with an embodiment of the invention;

FIG. 17 is a signaling diagram for closed-loop MIMO communicationbetween a BS and a wireless terminal according to an embodiment of theinvention;

FIG. 18 is a flow chart for a method of a BS allocating uplink resourcesfor closed-loop MIMO communication between the ES and a wirelessterminal in accordance with an embodiment of the invention; and

FIG. 19 is a signaling diagram for closed-loop MIMO communicationbetween a BS and a wireless terminal according to another embodiment ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order to facilitate downlink data transmission by a base station,some feedback information, such as C/I (carrier-to-interference)measurements, and/or wireless terminal indications, such asMIMO/permutation modes, are sent from a wireless terminal. The MAC layerof a network can be used to facilitate this feedback of information.

For the purposes of providing context for embodiments of the inventionfor use in a communication system, FIG. 1 shows a base stationcontroller (BSC) 10 which controls wireless communications withinmultiple cells 12, which cells are served by corresponding base stations(BS) 14. In general, each base station 14 facilitates communicationsusing OFDM with mobile and/or wireless terminals 16, which are withinthe cell 12 associated with the corresponding base station 14. Themovement of the mobile terminals 16 in relation to the base stations 14results in significant fluctuation in channel conditions. Asillustrated, the base stations 14 and mobile terminals 16 may includemultiple antennas to provide spatial diversity for communications.

A high level overview of the mobile terminals 16 and base stations 14upon which aspects of the present invention are implemented is providedprior to delving into the structural and functional details of thepreferred embodiments. With reference to FIG. 2, a base station 14 isillustrated. The base station 14 generally includes a control system 20,a baseband processor 22, transmit circuitry 24, receive circuitry 26,multiple antennas 28, and a network interface 30. The receive circuitry26 receives radio frequency signals bearing information from one or moreremote transmitters provided by mobile terminals 16 (illustrated in FIG.1). Preferably, a low noise amplifier and a filter (not shown) cooperateto amplify and remove broadband interference from the signal forprocessing. Downconversion and digitization circuitry (not shown) willthen downconvert the filtered, received signal to an intermediate orbaseband frequency signal, which is then digitized into one or moredigital streams.

The baseband processor 22 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. As such, the baseband processor 22 is generallyimplemented in one or more digital signal processors (DSPs) orapplication-specific integrated circuits (ASICs). The receivedinformation is then sent across a wireless network via the networkinterface 30 or transmitted to another mobile terminal 16 serviced bythe base station 14.

On the transmit side, the baseband processor 22 receives digitized data,which may represent voice, data, or control information, from thenetwork interface 30 under the control of control system 20, and encodesthe data for transmission. The encoded data is output to the transmitcircuitry 24, where it is modulated by a carrier signal having a desiredtransmit frequency or frequencies. A power amplifier (not shown) willamplify the modulated carrier signal to a level appropriate fortransmission, and deliver the modulated carrier signal to the antennas28 through a matching network (not shown). Modulation and processingdetails are described in greater detail below.

With reference to FIG. 3, a mobile terminal 16 configured according toone embodiment of the present invention is illustrated. Similarly to thebase station 14, the mobile terminal 16 will include a control system32, a baseband processor 34, transmit circuitry 36, receive circuitry38, multiple antennas 40, and user interface circuitry 42. The receivecircuitry 38 receives radio frequency signals bearing information fromone or more base stations 14. Preferably, a low noise amplifier and afilter (not shown) cooperate to amplify and remove broadbandinterference from the signal for processing. Downconversion anddigitization circuitry (not shown) will then downconvert the filtered,received signal to an intermediate or baseband frequency signal, whichis then digitized into one or more digital streams.

The baseband processor 34 processes the digitized received signal toextract the information or data bits conveyed in the received signal.This processing typically comprises demodulation, decoding, and errorcorrection operations. The baseband processor 34 is generallyimplemented in one or more digital signal processors (DSPs) andapplication specific integrated circuits (ASICs).

For transmission, the baseband processor 34 receives digitized data,which may represent voice, data, or control information, from thecontrol system 32, which it encodes for transmission. The encoded datais output to the transmit circuitry 36, where it is used by a modulatorto modulate a carrier signal that is at a desired transmit frequency orfrequencies. A power amplifier (not shown) will amplify the modulatedcarrier signal to a level appropriate for transmission, and deliver themodulated carrier signal to the antennas 40 through a matching network(not shown). Various modulation and processing techniques available tothose skilled in the art are used for signal transmission between themobile terminal and the base station.

In OFDM modulation, the transmission band is divided into multiple,orthogonal carrier waves. Each carrier wave is modulated according tothe digital data to be transmitted. Because OFDM divides thetransmission band into multiple is carriers, the bandwidth per carrierdecreases and the modulation time per carrier increases. Since themultiple carriers are transmitted in parallel, the transmission rate forthe digital data, or symbols, on any given carrier is lower than when asingle carrier is used.

OFDM modulation utilizes the performance of an Inverse Fast FourierTransform (IFFT) on the information to be transmitted. For demodulation,the performance of a Fast Fourier Transform (FFT) on the received signalrecovers the transmitted information. In practice, the IFFT and FFT areprovided by digital signal processing carrying out an Inverse DiscreteFourier Transform (IDFT) and Discrete Fourier Transform (DFT),respectively. Accordingly, the characterizing feature of OEDM modulationis that orthogonal carrier waves are generated for multiple bands withina transmission channel. The modulated signals are digital signals havinga relatively low transmission rate and capable of staying within theirrespective bands. The individual carrier waves are not modulateddirectly by the digital signals. Instead, all carrier waves aremodulated at once by IFFT processing.

In operation, OFDM is preferably used for at least downlink transmissionfrom the base stations 14 to the mobile terminals 16. Each base station14 is equipped with “n” transmit antennas 28, and each mobile terminal16 is equipped with “m” receive antennas 40. Notably, the respectiveantennas can be used for reception and transmission using appropriateduplexers or switches and are so labeled only for clarity.

With reference to FIG. 4, a logical OFDM transmission architecture willbe described. Initially, the base station controller 10 will send datato be transmitted to various mobile terminals 16 to the base station 14.The base station 14 may use the channel quality indicators (CQIs)associated with the mobile terminals to schedule the data fortransmission as well as select appropriate coding and modulation fortransmitting the scheduled data. The CQIs may be directly from themobile terminals 16 or determined at the base station 14 based oninformation provided by the mobile terminals 16. In either case, the CQIfor each mobile terminal 16 is a function of the degree to which thechannel amplitude (or response) varies across the OFDM frequency band.

Scheduled data 44, which is a stream of bits, is scrambled in a mannerreducing the peak-to-average power-ratio associated with the data usingdata scrambling logic 46. A cyclic redundancy check (CRC) for thescrambled data is determined and appended to the scrambled data usingCRC adding logic 48. Next, channel coding is performed using channelencoder logic 50 to effectively add redundancy to the data to facilitaterecovery and error correction at the mobile terminal 16. Again, thechannel coding for a particular mobile terminal 16 is based on the CQI.In some implementations, the channel encoder logic 50 uses known Turboencoding techniques. The encoded data is then processed by rate matchinglogic 52 to compensate for the data expansion associated with encoding.

S Bit interleaver logic 54 systematically reorders the bits in theencoded data to minimize the loss of consecutive data bits. Theresultant data bits are systematically mapped into corresponding symbolsdepending on the chosen baseband modulation by mapping logic 56.Preferably, Quadrature Amplitude Modulation (QAM) or Quadrature PhaseShift Key (QPSK) modulation is used. The degree of modulation ispreferably chosen based on the CQI for the particular mobile terminal.The symbols may be systematically reordered to further bolster theimmunity of the transmitted signal to periodic data loss caused byfrequency selective fading using symbol interleaver logic 58.

At this point, groups of bits have been mapped into symbols representinglocations in an amplitude and phase constellation. When spatialdiversity is desired, blocks of symbols are then processed by space-timeblock code (STC) encoder logic 60, which modifies the symbols in afashion making the transmitted signals more resistant to interferenceand more readily decoded at a mobile terminal 16. The STC encoder logic60 will process the incoming symbols and provide “n” outputscorresponding to the number of transmit antennas 28 for the base station14. The control system 20 and/or baseband processor 22 as describedabove with respect to FIG. 2 will provide a mapping control signal tocontrol STC encoding. At this point, assume the symbols for the “n”outputs are representative of the data to be transmitted and capable ofbeing recovered by the mobile terminal 16.

For the present example, assume the base station 14 has two antennas 28(n=2) and the STC encoder logic 60 provides two output streams ofsymbols. Accordingly, each of the symbol streams output by the STCencoder logic 60 is sent to a corresponding IFFT processor 62,illustrated separately for ease of understanding. Those skilled in theart will recognize that one or more processors may be used to providesuch digital signal processing, alone or in combination with otherprocessing described herein. The IFFT processors 62 will preferablyoperate on the respective symbols to provide an inverse FourierTransform. The output of the IFFT processors 62 provides symbols in thetime domain. The time domain symbols are grouped into frames, which areassociated with a prefix by prefix insertion logic 64. Each of theresultant signals is up-converted in the digital domain to anintermediate frequency and converted to an analog signal via thecorresponding digital up-converoion (DUC) and digital-to-analog (D/A)conversion circuitry 66. The resultant (analog) signals are thensimultaneously modulated at the desired RF frequency, amplified, andtransmitted via the RF circuitry 68 and antennas 28, Notably, pilotsignals known by the intended mobile terminal 16 are scattered among thesub-carriers. The mobile terminal 16, which is discussed in detailbelow, will use the pilot signals for channel estimation.

Reference is now made to FIG. 5 to illustrate reception of thetransmitted signals by a mobile terminal 16. Upon arrival of thetransmitted signals at each of the antennas 40 of the mobile terminal16, the respective signals are demodulated and amplified bycorresponding RF circuitry 70. For the sake of conciseness and clarity,only one of the two receive paths is described and illustrated indetail, Analog-to-digital (A/D) converter and down-conversion circuitry72 digitizes and downconverts the analog signal for digital processing.The resultant digitized signal may be used by automatic gain controlcircuitry (AGC) 74 to control the grain of the amplifiers in the RFcircuitry 70 based on the received signal level.

Initially, the digitized signal is provided to synchronization logic 76,which includes coarse synchronization logic 78, which buffers severalOFDM symbols and calculates an auto-correlation between the twosuccessive OFDM symbols. A resultant time index corresponding to themaximum of the correlation result determines a fine synchronizationSearch window, which is used by fine Synchronization logic 80 todetermine a precise framing starting position based on the headers. Theoutput of the fine synchronization logic 80 facilitates frameacquisition by frame alignment logic 84. Proper framing alignment isimportant so that subsequent FFT processing provides an accurateconversion from the time domain to the frequency domain. The finesynchronization algorithm is based on the correlation between thereceived pilot signals carried by the headers and a local copy of theknown pilot data. Once frame alignment acquisition occurs, the prefix ofthe OFDM symbol is removed with prefix removal logic 86 and resultantsamples are sent to frequency offset correction logic 88, whichcompensates for the system frequency offset caused by the unmatchedlocal oscillators in the transmitter and the receiver. Preferably, thesynchronization logic 76 includes frequency offset and clock estimationlogic 82, which is based on the headers to help estimate such effects onthe transmitted signal and provide those estimations to the correctionlogic 88 to properly process OFDM symbols.

At this point, the OFDM symbols in the time domain are ready forconversion to the frequency domain using FFT processing logic 90. Theresults are frequency domain symbols, which are sent to processing logic92. The processing logic 92 extracts the scattered pilot signal usingscattered pilot extraction logic 94, determines a channel estimate basedon the extracted pilot signal using channel estimation logic 96, andprovides channel responses for all sub-carriers using channelreconstruction logic 98. In order to determine a channel response foreach of the sub-carriers, the pilot signal is essentially multiple pilotsymbols that are scattered among the data symbols throughout the OFDMsub-carriers in a known pattern in both time and frequency. FIG. 15illustrates an exemplary scattering of pilot symbols among availablesub-carriers over a given time and frequency plot in an OFDMenvironment. Continuing with FIG. 5, the processing logic compares thereceived pilot symbols with the pilot symbols that are expected incertain sub-carriers at certain times to determine a channel responsefor the sub-carriers in which pilot symbols were transmitted. Theresults are interpolated to estimate a channel response for most, if notall, of the remaining sub-carriers for which pilot symbols were notprovided. The actual and interpolated channel responses are used toestimate an overall channel response, which includes the channelresponses for most, if not all, of the sub-carriers in the OFDM channel.

The frequency domain symbols and channel reconstruction information,which are derived from the channel responses for each receive path areprovided to an STC decoder 100, which provides STC decoding on bothreceived paths to recover the transmitted symbols. The channelreconstruction information provides equalization information to the STCdecoder 100 sufficient to remove the effects of the transmission channelwhen processing the respective frequency domain symbols

The recovered symbols are placed back in order using symbolde-interleaver logic 102, which corresponds to the symbol interleaverlogic 58 of the transmitter. The de-interleaved symbols are thendemodulated or de-mapped to a corresponding bitstream using de-mappinglogic 104. The bits are then de-interleaved using bit de-interleaverlogic 106, which corresponds to the bit interleaver logic 54 of thetransmitter architecture. The de-interleaved bits are then processed byrate de-matching logic 108 and presented to channel decoder logic 110 torecover the initially scrambled data and the CRC checksum. Accordingly,CRC logic 112 removes the CRC checksum, checks the scrambled data intraditional fashion, and provides it to the de-scrambling logic 114 forde-scrambling using the known base station de-scrambling code to recoverthe originally transmitted data 116.

In parallel to recovering the data 116, a CQI, or at least informationsufficient to create a CQI at the base station 14, is determined andtransmitted to the base station 14. As noted above, the CQI may be afunction of the carrier-to-interference ratio (CR), as well as thedegree to which the channel response varies across the varioussub-carriers in the OFDM frequency band. For this embodiment, thechannel gain for each sub-carrier in the OFDM frequency band being usedto transmit information is compared, relative to one another todetermine the degree to which the channel gain varies across the OFDMfrequency band. Although numerous techniques are available to measurethe degree of variation, one technique is to calculate the standarddeviation of the channel gain for each sub-carrier throughout the OFDMfrequency band being used to transmit data.

FIGS. 1 to 5 provide one specific example of a communication system thatcould be used to implement embodiments of the invention. It is to beunderstood that embodiments of the invention can be implemented withcommunications systems having architectures that are different than thespecific example, but that operate in a manner consistent with theimplementation of the embodiments as described herein.

The MAC (media access control) layer is used to enable features in thephysical (PHY) layer in an OFDM air interface framework. Frames are aformat used to transmit data over the air interface between basestations (RS) and wireless terminals. A wireless terminal is any OFDMcapable wireless device and may be fixed location, nomadic or mobile,for example a cellular telephone, computer with a wireless modem, orPDA. Some types of information elements (IE) are included in the frameto provide a structure within the frame for defining where downlink anduplink information are located within the frame.

FIG. 6 shows a schematic diagram of an example frame used in conjunctionwith embodiments of the invention. Details are shown for a framelabelled “Frame A”, generally indicated at 205, which is preceded byFrame “N−1” and followed by “Frame N+1”, all forming part of an ongoingsequence of frames. The frame has a two dimensional appearance which isrepresented in terms of a rows and columns. The rows are designated bylogical subchannel numbers L,L+1, . . . L+15 and the columns aredesignated by OFDM symbol numbers M,M+1, . . . M+15 Logical subchannelsare designated groupings of active subcarriers. Active subcarriers areany one of data subcarriers for data transmission, pilot subcarriers forsynchronization, or subcarriers that do nor involve direct transmission,but are used as transition guards between parts of the frame. In theframe N of FIG. 6, a preamble 210 is included in a first OFDM symbol M.A second OFDM symbol M+1 and a third OFDM symbol M+2 include both adownlink (DL) mapping component 212 including one or more informationelements 213 and an uplink (UL) mapping component 214 including one ormore information elements 215. Other broadcast messages (not shown) maybe included as well. Subsequent OFDM symbols M+3 through M+9 contain aDL subframe 217. The DL subframe 217 contains DL information allocatedto regions 216 of the DL subframe 217 to be transmitted to one or moremobile terminals. Following the DL subframe 217 is atransmit/receive/transition guard (TTG) 218, shown during OFDM symbolperiod M+10. After the TTG 218 is a UL subframe 219 containing ULinformation allocated to designated regions 224 of the UL subframe to betransmitted back to the base station. The UL subframe 219 also includesfast feedback channels 222 that are used to allow the mobile terminal toreport information to the base station. For example a fast feedbackchannel 222 can be designated as a channel to indicate the air interfacechannel quality between the base station and the mobile terminal.Following the UL subframe 219 is a receive/transmit transition guard(RTG) 220. Frames N−1 and N+1 have a similar composition.

Regions 216 of the DL subframe 217 contain MAC protocol data units(PDU), Regions 224 of the UL subframe 219 also contain MAC PDUs. MACPDUs are known to include some or all of the following: a MAC header,MAC subheaders and a MAC payload.

The data frame of FIG. 6 is an example of a time division duplex (TDD)data frame. It is to be understood that embodiments of the invention arealso applicable to frequency division duplex (FDD) operation.

The illustrated frame structure is a specific example. The preamble,mapping components, DL subframe and UL subframe may be implemented usingan implementation specific number of OFDM symbols, with implementationspecific guard bands. The number and definition of OFDM subchannels isalso an implementation detail. The layout sequence of the various fieldscan also be varied.

Feedback Methodologies

In general, optimized downlink (DL) operations between the BS and themobile terminal utilize feedback from the mobile terminal, commonlyknown to those skilled in the art and therefore referred to hereafter,as a “Mobile Subscriber Station” (MSS). While Subscriber station denotesa device subscribing to a service, it is to be understood that the moregeneral wireless terminal, to which embodiments of the invention apply,may not be a subscriber to any services and may not necessarily bemobile. Those types of feedback include DL channel quality indication(CQI) feedback, DL MIMO (multiple input multiple output) mode andpermutation selection, physical channel report, etc. There are alsoother feedback related to the uplink (UL) operation, such as the MSS ULtransmit power headroom.

In order to facilitate downlink data transmission, some information,such as c/1 measurements (received signal power divided by the noiseplus interference power) and MSS indications, such as MIMO permutationmodes is transmitted from the MSS to the BS.

In the IEEE 802.16e standard a fast-feedback channel is introduced toenable such UL transmission. The fast feedback channel utilizes adedicated CQI channel to transmit a limited amount of feedbackinformation in addition to the CQIs. Two types of fast feedbackoperations are established in which:

1) a unicast Fait-Feedback allocation subheader is utilized to let theMSS feedback one of four types of information on a temporarily allocatedfast-feedback channel; and

2) a broadcast channel allocation information element (IE) is utilizedto allocate a dedicated feedback channel with periodic opportunity forenabling the MSS to provide the BS with an indication of its MIMOrelated feedback.

The two above-described approaches provide quasi periodic opportunity toenable the MSS to provide its indication and feedback. Furtherdescription regarding these types of fast feedback operations is foundin U.S. patent application Ser. No. 11/547,561 filed Oct. 5, 2006, nowU.S. Pat. No. 7,630,356, which is assigned to the assignee of thepresent application and is incorporated herein by reference.

In some situations, if the MSS needs to inform its intention based onsome real-time requirements and needs the BS to have a quick reaction(e.g., fast anchor BS switching, MIMO mode switching, UL resourcerequest and etc), the above two approaches may not be efficient ways ofperforming this task, especially if the MSS has a dedicated feedbackchannel assigned for periodic reporting and the indication from the MSSis not expected to change very frequently so the period is set to a longduration.

In some embodiments of the present invention, it is assumed that eachMSS has a dedicated feedback channel. An example of such a dedicatedfeedback channel is a channel quality indication channel (CQICH) whichallows the MSS to provide feedback to the SS regarding the quality ofthe communication channel between the BS and MSS. The dedicated channelmay for example, be allocated by a CQICH allocation information element(CQICH Alloc IE) as described in U.S. patent application Ser. No.11/547,561 filed Oct. 5, 2006, now U.S. Pat. No. 7,630,356, or bychannel allocation IEs described below. or by channel allocation IEsdescribed below.

In some embodiments, the dedicated feedback channel allocated by the SSallows for transmission of 4 bits of feedback information. An enhanceddedicated feedback channel allows for transmission of 6 bits, Moregenerally, the number of bits transmitted by the feedback channel may beother than the 4 bits or 6 bits specifically mentioned above. However,preferably the number of bits is less than 10 bits.

A first embodiment of enabling feedback will now be described inrelation to FIG. 7. In the particular embodiment described, the MSSsends periodic C/I reports to the BS at 600. The periodic reports aresent on the dedicated channel. At a subsequent point in time, indicatedat 610, the MSS autonomously indicates to the BS its intention to sendfeedback information by transmitting a pre-reserved feedback payloadcode on the dedicated feedback channel, for example 1111, to the BS.

In response to this pre-reserved feedback payload code, the BS sends theMSS an information element (IE), indicated at 620, that allocates uplinkresources for the MSS to send MSS feedback containing the feedbackinformation. In some embodiments the IE may be a “MIMO UL Basic” IE asdescribed in U.S. patent application Ser. No. 11/547,561 filed Oct. 5,2006, now U.S. Pat. No. 7,630,356, used for allocating UL transmissionresources. The BS sends the uplink resource allocation IE within ageneral uplink resource allocation mapping component portion of the dataframe, such an mapping component 214 in FIG. 6. In some instances, theMSS feedback includes information such as basic connectionidentification (CAP), feedback type and feedback content. The MSS thensends the MSS feedback information to the BS over the allocated uplinkresource in a MAC PDU at 630. The MAC PDU allocated as an uplinkresource is found in regions 224 of the UL subframe 219 in the dataframe 205 of FIG. 6 as described above. The MSS sending the MSS feedbackinformation 630 may occur in the same data frame as the uplink resourceallocation IE is sent 620 or it may send the MSS feedback information ina subsequent data frame.

The MSS feedback information in the above signaling example is sent inthe form of any one of a 1) feedback header, 2) a feedback mini-headeror 3) a subheader in the MAC PDU, as will be described in more detailbelow. The feedback header and the feedback mini-header are particularexamples of a more general MAC PDU header. The feedback header andfeedback mini-header are portions of the MAC PDU that typically precedethe MAC payload. In some embodiments, they contain information specificto the PDU related to the contents of the MAC PDU, for example aconnection identifier (CID) for a communication link between the BS anda specific MSS. The feedback subheader is a particular example of a moregeneral MAC PDU subheader. The feedback subheader is another componentthat may be included in a MAC PDU. A subheader is typically locatedbetween the MAC PDU header and the MAC PDU payload and can be used fortransmission of information between the BS and the MSS

The above-described embodiment can also be used as a preliminary stepfor the MSS to request additional uplink resources. In response toreceiving the pre-reserved feedback payload code, the BS allocates anuplink resource of a particular size, for example 6 bytes. Instead ofusing the 6 bytes to transmit feedback information, the MSS may use the6 byte allocation to Transmit a request for a more appropriate sized ULtransmit resource. One example of such a request is a Bandwidth Requestheader.

In some embodiments, the MS sends the pre-reserved payload code wheneverit has feedback information to send to the SS.

The pre-reserved payload code is any particular N-bit payload value thatis established to be recognized as the indication that the MSS desiresto send feedback information, where “N” is the number of bits used fortransmission on the feedback channel.

When the feedback channel used is enabled for 4 bits, the pre-reservedpayload bits are set and maintained in an uplink channel description(UCD) as a specific channel encoding value. Preferably the N-bit payloadvalue is not to be all zeroes. Preferably, when the feedback channel isthe enhanced fast feedback channel that is enabled for C bits, thepre-reserved code is Ob11110.

If the MSS supports the feedback method by using the pre-reserved N-bitpayload code and a feedback header, a value “M” is defined as thepre-reserved N-bit payload code in the UCD. To avoid a situation wherethe pre-reserved payload code conflicts with a calculated CQI that istransmitted on the same channel as the pre-reserved payload code, if acalculated CQI payload value is found to be equal to the value “M” theMSS sets the CQI payload bits to a value equal to “M−1” instead of Inanother embodiment also having a dedicated feedback channel, illustratedby way of example in FIG. 8, the ES uses an unsolicited polling methodto indicate its request for feedback information. The polling methodinvolves using an IE, such as the UL IE 215 in FIG. 6, sent by the DS toschedule MSS feedback information transmission by the MSS. An example ofa particular IE in a “Feedback polling” IE that will be described inmore detail below. The SS sends the polling IE at 700, which indicatesthe feedback type desired by the BS to the MSS within the more generaluplink resource allocation mapping component portion of the data frame,such as mapping component 214 in FIG. 6. The MSS uses the dedicatedfeedback channel to report the desired feedback information in the nextframe, indicated at 710. In some embodiments, the process of polling andreporting occurs as often as desired by the ES.

In some embodiments, the MSS does not have a dedicated feedback channelallocated for feedback transmission to the ES. Therefore, the RSallocates a temporary feedback channel to be used by the MSS fortransmitting feedback information.

With reference to FIG. 9, in a first such embodiment with no dedicatedfeedback channel, the SS uses an unsolicited polling method by using anIE sent by the BS to schedule DSS feedback transmission by the MSS.Similar to the polling IE described above for the case where a dedicatedchannel does exist, the polling IE in this embodiment includes thedesired feedback type for the MSS to report. In addition, the BS alsoallocates a temporary feedback channel in the data frame to be used fortransmission of the MSS feedback. The IS transmits the polling IE, shownat 800, which indicates the feedback type expected by the BS as well asan identification of the temporarily allocated feedback channel. The MSSuses the temporarily allocated feedback channel to report the desiredfeedback information requested by the BS in the next frame, as indicatedat 810. The polling IE used in this example is the “Feedback polling”IE, which will be described in more detail below.

In FIGS. 8 and 9, the MSS sending the MSS feedback information on thededicated or temporarily allocated channel may occur in the same dataframe as the polling IE is sent or it may send the MSS feedbackinformation in a subsequent data frame.

In the examples of FIGS. 8 and 9, instead of transmitting a pollingindication to the MSS using the polling 12, the BS may use a fastfeedback subheader, as described in U.S. patent application Ser. No.11/547,561 filed Oct. 5, 2006, now U.S. Pat. No. 7,630,356, to indicatethe type of feedback requested by the BS and the location of the uplinkresources (either a dedicated channel or a temporarily allocatedchannel) for the MSS to transmit the feedback requested by the BS.

With reference to FIG. 10, another embodiment in which there is nodedicated feedback channel will now be described. The BS uses anotherform of an unsolicited polling method to enable the MSS to send MSSfeedback information. The BS uses an uplink resource allocation IE, forexample the “MIMO UL Basic” IE described above to allocate ULtransmission resources for the MSS to transmit feedback information onas indicated at 900, instead of sending the polling IE as in thepreviously described embodiment. The BS sends the uplink resourceallocation IE within a more general uplink resource allocation mappingcomponent portion of the data frame. Allocating the UL transmissionresources includes the IE transmitting a location of the UL transmissionresources in the data frame. The MSS uses the UL resources allocated bythe uplink resource allocation IE to transmit a MAC PDU containing theMSS feedback information to the BS as indicated at 910. The MSS sendingthe MSS feedback information 910 may occur in the same data frame as theuplink resource allocation JR is sent 900 or it may send the MSSfeedback information in a subsequent data frame.

The MSS feedback information in the above signaling example is sent inthe form of any one of a feedback header, a feedback mini-header or asub-header in the MAC PDU, as will be described in more detail below.

One advantage of the above embodiments is to enable quick reaction basedon a real-time requirement, such as fast anchor BS switching, fast MIMOmode switching or timely X resource allocation for UL traffic.

“Feedback Polling” IE

The periodic polling from the BS in the form of an IE transmits to theMSS a number of allocations for a frame. For each allocation the BSindicates whether a dedicated channel is previously assigned or afeedback channel needs to be temporarily assigned. If the dedicatedchannel is previously assigned, the BS transmits an identification ofthe dedicated channel on which feedback is to be transmitted. If thefeedback channel needs to be temporarily assigned, the BS identifies alocation of a feedback channel to be used for transmitting feedback typeand feedback content in an uplink portion of the frame. The BS thenindicates the feedback type on the assigned feedback channel.

An example of syntax for the scheduling TR used for unsolicited pollingof the MSS described above with respect to FIGS. 8 and 9 is shown inTable 1 identified as the “Feedback polling” IE. In some embodiments,the “Feedback polling” IE is designed so that it can be used whether ornot there is a dedicated channel. The “Feedback polling” IE of table 1uses a “Feedback channel assigned indicator” field to indicate whether afeedback channel is already dedicated or a feedback channel needs to betemporarily allocated. How the “Feedback channel assigned indicator”field is set determines if the RS needs to allocate a temporary feedbackchannel or not. If a feedback channel needs to be temporarily allocated,then the “Feedback channel assigned indicator” field bit is set equal to“0”, so that provision will be made for this action. If the feedbackchannel does not need to be temporarily allocated, then the “Feedbackchannel assigned indicator” field bit is set equal to “1”, and thededicated feedback channel is appropriately identified using the“channel quality indicator ID (CQICH ID)” field. Once the conditions forthe feedback channel are established, the feedback type desired by theBS is set using the “Feedback type” field.

TABLE 1 Feedback polling IE format Size in Syntax bits Notes Feedbackpolling IE( ) {  Extended UIUC 4 Identifies type of IE  Length 4 Lengthof the message in bytes  Num Allocations 4 Number of allocations in thisIE  for (i = 0; i < Num Allocation poll; i++) {   Feedback channel 1 0:BS is polling a MSS assigned indicator who has no dedicated feedbackchannel assigned 1: BS is polling a MSS who has a dedicated feedbackchannel assigned   if (feedback channel assigned indicator == 0 ) {   CID 16 Basic ID of the polled MSS    Feedback channel 6 Index to thefast offset feedback channel region marked by UIUC   }   else {    CQICHID Variable Assigned by using CQICH_alloc_IE   }   Feedback type 4  } }

The “Extended UIUC (uplink interval usage code)” field of Table 1 isused to associate a code value to identify a particular type of IE. Forexample, the “Feedback polling” IE in Table 1 might have “ExtendedUIUC”=06. Other IF have different respective Extended UIUC values. Thevalue provided in Table 1 or values in subsequent tables below are mereexamples of code values that could be used and it is to be understoodthat the code values assigned, and the number of bits used to representthe codes values could be varied according to a desired usage.

The values in the “Size” column of Table 1 refer to a number of bitsused to represent the element of each respective field. It is to beunderstood that these values are but one example for each respectivefield. In some embodiments, the number of hits can be greater or lessthan what is represented in Table 1. For example, the number of bits inany of the fields may be desired to be less than the values representedabove to reduce an overall IE size, and therefore reduces an overalloverhead of the frame. Conversely, the number of bits in any of thefields may be greater than the values represented above at an acceptablecost of increasing the overall overhead of the frame.

Examples of feedback types used in the “Feedback type” field are foundin Table 2. More generally, other types of feedback type and feedbackcontent that are consistent with the intention of the invention asdescribed herein, but not specifically included are to be consideredwithin the scope of the present invention.

TABLE 2 Feedback Type and Feedback content Feedback Type Feedbackcontents Description 0b0000 MIMO feedback type MIMO mode and(0b0000-0110 in Table 4 permuatation Feedback below) + feedback payload0b0001 DL average CQI (5 bits) 5 bits CQI feedback 0b0010 Antenna index(2 bits) + MIMO coefficients MIMO coefficients (5 feedback bits) 0b0011Preferred-DIUC (4 bits) Preferred DL channel DIUC feedback 0b0100UL-TX-Power (7 bits) UP transmission power 0b0101 Preferred DIUC(4bits) + UL- PHY channel feedback TX-Power (7 bits) + UL- headroom (6bits) 0b0110 Number of groups, A (2 CQIs of antenna groups bits) + Aoccurrences of ‘group index (2 bits) + CQI (5 bits)’ 0b0111 Number ofbands, B (2 Multiple Band of CQI bits) + B occurrences of ‘band index (6bits) + CQI (5 bits)’ 0b1000 Number of feedback types, Multiple types ofC (2 bits) + C feedback occurrences of ‘feedback type (4bits) + feedbackcontent (variable)’ 0b1001-0b111 Reserved

The binary values in the “Feedback type” column of Table 2 areassociated with particular selectable options related to those fields.It is to be understood that each particular binary value is but oneexample for each particular option and a particular option can berepresented by any appropriate binary value having any reasonable numberof bits. More generally, other types of feedback type and feedbackcontent that are consistent with the intention of the invention asdescribed herein, but not specifically included are to be consideredwithin the scope of the present invention.

Table 3a shows an alternative “Feedback polling” IE format to that shownin Table 1, in accordance with another embodiment of the invention.

TABLE 3a Feedback polling IE format Size in Syntax bits Notes Feedbackpolling IE( ){  Extended UIUC 4 Identifies type of IE  Length 4 Lengthin bytes of following fields  for (i=0; i < Num Allocations; i++) {  Basic CID   UIUC   Feedback type 6   Allocation offset 3 The ULfeedback shall be transmitted in the frame which is 0-8 frame delayrelative to the current frame.   Duration 10 In OFDM slots  } }

In the “Feedback polling” IE of Table 3a, the “Allocation Offset” fieldindicates when the MSS in to transmit feedback information relative tothe current frame.

Table 3b shows another alternative “Feedback polling” IE format to thatshown in Table 1, in accordance with another embodiment of theinvention.

TABLE 3b Feedback polling IE format Size in Syntax bits Notes Feedbackpolling IE( ) {  Extended UIUC 4 Identifies type of IE  Length 8 Lengthof the message in bytes  Num Allocations 4 Number of allocations in thisIE  Dedicated UL Allocation 1 0: No dedicated UL Included resource isallocated in feedback polling IE. BS should allocate UL resource throughthe UL map IE at each designated transmitting frame defined by this IE.1: Dedicated UL resource is included in the IE  Reserved 3 Set to zero for (i = 0; i < Num Allocations ; i++) {   Basic CID 16 Basic ID of thepolled MSS   Allocation Duration (d) The allocation is valid for 10x2dframe starting from the frame defined by Frame offset If d=0b000, thepre- scheduled Feedback header transmission is released If d=0b111, thepre- scheduled Feedback header transmission shall be valid until the BScommands to release it    If (d ! = 000){     Feedback type 4     Frameoffset 6 The offset (in units of frames) from the current frame in whichthe first feedback header shall be transmitted on the allocated ULresource. The start value of frame offset shall be 1     Period (p) 2The UL resource region is dedicated to the MS in every 2^(P) frame    If (Dedicated UL Allocation Included == 1){      UIUC 4      OFDMAsymbol offset 8      Subchannel offset 7      Duration 3 In OFDMA slots     Repetition coding 2 0b00 - No repetition indication coding 0b01 -Repetition coding of 2 used 0b10 - Repetition coding of 4 used 0b11 -Repetition coding of 6 used     }    }   }  Padding bits }

Table 3b corresponds generally to a method described in the flow chartof FIG. 11. At step 1100, the base station transmits a total number offeedback resource allocations for a data frame. At step 1110 anindication if feedback resources are to be dedicated as a part of themethod is also transmitted by the base station. As indicated at 1120 alooping function is initiated for each feedback resource allocation ofthe total number of feedback resource allocations. At step 1130, thebase station transmits an identifier for the wireless terminal for whichthe feedback resource allocation is occurring. At step 1140, it isdetermined if the feedback resource is currently not released. If thefeedback resource is currently not released, then at step 1150 the basestation transmits an indication of feedback type requested by the basestation and a location of a subsequent data frame with reference to thecurrent data frame indicating when feedback information requested by thebase station will be received on an allocated feedback resource. At step1160, if feedback resources are to be dedicated as a part of the methodaccording to step 1110, a feedback resource is allocated by transmittinglocation information for the feedback resource,

Feedback Header

One example of fast feedback currently known in wireless OFDM MEMOsystem is a DL FAST_FEEDBACK subheader (described in more detail in U.S.patent application Ser. No. 11/547,561 filed Oct. 5, 2006, now U.S. Pat.No. 7,630,356) used by the BS to poll a MSS to provide up to four typesof feedback on the fast feedback channel. To support MIMO channelrelated feedback, and feedback to support other aspects of UL operation,however, a greater number of feedback types are desired to be defined aswell as an associated additional capacity for transmitting feedbackcontent for these additional feedback types. A new polling signalingformat is desired to be defined to accommodate more than the existingfour types of feedback. In some embodiments of the present invention,including in particular the feedback header, the MSS is able to feedbacka greater capacity of information at one time than the previouslyidentified methods of performing feedback, such as using the DLFAST_FEEDBACK subheader.

The feedback header of the present invention sent by the MSS in responseto an unsolicited polling IE from the BS has fields to identify it as afeedback header, identify the type of feedback and include feedbackcontents. Some examples of types of feedback and feedback contents arefound in Tables 2 and 4.

TABLE 4 Encoding of payload bits for “MIMO feedback type” ValueDescription 0b0000 STTD and PUSC/FUSC permutation 0b0001 STTD andadjacent-subcarrier permutation 0b0010 SM and PUSC/FUSC permutation0b0011 SM and adjacent-subcarrier permutation 0b0100 Close-loop SM andPUSC/FUSC permutation 0b0101 Close-loop SM and adjacent subcarrierpermutation 0b0110 Close-loop SM + beamforming and adjacent subcarrierpermutation 0b0111 TEMP_BS_ID of expected anchor BS (TEMP_BS_ID wasassigned in MOB_BSHO_REQ/RSP when the BS was added to the active set ofa MSS) Others Reserved

The binary values in the “Value” column of Table 4 are associated withparticular selectable options related to those fields. It is to beunderstood that each particular binary value is but one example for eachparticular option and a particular option can be represented by anyappropriate binary value having any reasonable number of bite. Inaddition, encoding of other types of feedback, not specificallydescribed herein, can be assigned to the reserved bit values.

An embodiment of a feedback header will now be described with respect toFIG. 12. FIG. 12 shows a portion of a feedback PDU (protocol data unit),the portion being a feedback header 300. The feedback PDU is located inregions 224 of the UL subframe 219 in data frame 205 of FIG. 6. Thefeedback header 300 includes a “Header Type (HT)” field 310, an“Encryption Control (EC)” field 320, a “Normal feedback header/Minifeedback header indication (N/M)” field 330 and a “CID InclusionIndication (CII)” field 350. The remainder of the feedback header 300includes a “Feedback Content” field 360, a “Basic connectionidentification (CID) field 370 and a “Header Check Sequence (HCS)” field380.

An example of the feedback header 300 includes the following properties:

a) The length of the feedback header is 6 bytes (48 bits);

b) The “HT” field 310 is set equal to “1” and the “EC” field 320 is setequal to “1”. This combination of bits is used to indicate that theheader 300 is a feedback header;

c) The “N/M” field 330 as described below is set equal to “0” toindicate that this is a normal sized feedback header 300;

d) The “Feedback Type” field 340 is set according to the desiredfeedback type, for example the entries in Table 2 above;

e) The “CII” field 350 is set equal to “0” for the header with a CIDfield and set to 1 for the header without the CID field; and

f) The “Feedback Content” field 360 is filled with feedback informationto be supplied to the BS. For example, the feedback information may bebased on the “Feedback Content” entries in Table 2 associated with aparticular “Feedback Type”.

In FIG. 12, the number that is in brackets in each field is a number ofbits allocated to that field. For example, the number of bits in the“HT” filed is “1”, the number of bits in the Feedback Type” field is “4”and the number of bits in the “Feedback content field is “8”. In apreferred embodiment of the invention, the feedback header has 48 bitsas shown. However, more generally, the number of bits is variabledepending on the size of the feedback header desired. In someembodiments, the number of bits may still equal 48, but the distributionof bits may be allocated differently than shown.

Furthermore, in some embodiments not all of the fields illustrated inFIG. 12 are included in the feedback header and the resulting header isstill to be considered within the scope of the invention, for examplethere may be no “Basic CID” field 370.

In some situations, since the feedback header is sent using unicast ULresources assigned by the SS, the “Basic CID” field 370 in the feedbackheader 300 is redundant since the unicast UL resource uniquelyidentifies the MSS and will be sent by the MSS on a dedicated channel.Thus, the 16-bit “Basic CID” field 370 in the feedback header 300 can beremoved and the bit space used for sending more feedback information.

In accordance with an embodiment of the invention, FIG. 13 shows thefeedback header 301 without the “Basic CID” field 370. This allows moreroom for feedback content 360 to be transmitted. The other of thefeedback header fields are the same as feedback PDU 300. Similarly toFIG. 12, the numbers that are in brackets in each field represent thenumber of bite allocated to the field.

In addition to using the feedback header in response to the feedbackpolling IE or the UL resource allocation mapping IE, the feedback headercan be used in other scenarios when feedback information needs to besent by a MSS. For example, the MSS can autonomously send the feedbackheader to the BS by sending a bandwidth request ranging code and thensend the header after receiving a CDMA Allocation IE. In anotherexample, a MSS can autonomously send the feedback header to the SS bysending the header along with UL traffic.

Feedback Mini-header

According to another embodiment of the invention there is provided afeedback header of reduced size. According to one embodiment of theinvention this reduced size feedback PDU includes a feedback mini-headerand does not contain a payload. A reduced size feedback header inaccordance with an embodiment of the invention is shown in FIG. 14,generally indicated at 500. The reduced size feedback header 500includes a “HT” field 510, a “EC” field 520, a “N/M type” field 530. Theremainder of the reduced size header 500 includes a “Feedback Content”field 550, and a “HCS” field 560.

An example of the reduced size feedback header 500 has the followingproperties;

a) The length of the header 500 is 3 bytes (24 bits);

b) The “HT” field 510 is set to 1 and the “EC” field 520 is set to 1,the combination of which indicates that the header is a feedback header;

c) The “N/M” field 540 is set to 1 to indicate that this is a half-sizedFeedback header;

d) The “Feedback Type” field 540 is set according to the desiredfeedback type, for example the entries in Table 2 above; and

e) The “Feedback Content” 550 field is set accordingly, for examplebased on the entries in Table 2 in accordance with the selected value ofthe “Feedback Type” field.

When a MSS sends a feedback header on a unicast UL resource, the MSS maydecide the size of the feedback header (i.e. normal feedback header orreduced sized feedback mini-header) based on the feedback type and theamount of information to feed back.

For the feedback header, MSS report IS and the feedback mini-header,other types of feedback type and feedback content that are consistentwith the intention of the invention as described herein, but notspecifically included in Table 2 and 4 are to be considered within thescope of the present invention. Furthermore, while the bit size of the“Feedback Type” and “Feedback Content” fields is described as 4 and 8bits respectively, the number of bits in theses fields may be greaterthan or less than these numbers.

In a preferred embodiment of the invention, the feedback header has 24bits as shown however, more generally, the number of bits is variabledepending on the size of the feedback header desired. In someembodiments, the number of bits may still equal 24, but the distributionof bits may be allocated differently than shown.

Mini-Feedback Subheader

According to another embodiment of the invention the MSS can sendfeedback information to the BS in a mini-feedback subheader. Subheadersare part of a MAC PDU sent by the MSS to the BS that typically arelocated subsequent the header in the MAC feedback PDU. The subheadermost often occurs between the header and the content or payload of thePDU, but it may be located elsewhere in the PDU. An example of theformat of such a mini-feedback subheader is shown in Table 5.

TABLE 5 Mini-Feedback Subheader Name Size in bits Description FeedbackType 4 Type of feedback Feedback Content 12

Examples of the “Feedback type” and “Feedback Content” fields are foundin Tables 2 and 4. More generally, other types of feedback type andfeedback content that are consistent with the intention of the inventionas described herein, but not specifically included are to be consideredwithin the scope of the present invention.

MIMO transmission format and signalling apparatus are generalized toallow a variety MIMO schemes to operate by using the same air-interfacedesign. In some communications sessions basic transmission formatsinclude: (1) spatial multiplexing (SM) and (2) space-time transmitdiversity (STTD), with vector or matrix weighted full MIMO or sub-MIMOtransmission based on 2, 3 and 4 transmit antennas configurations, forexample.

The following schemes are also generalized to the multiple base stationtransmission.

In order to utilize a feedback channel, the feedback channel must firstbe allocated. An embodiment of the invention will now be described withrespect to FIG. 16. FIG. 16 illustrates a flow chart for a method ofdynamically allocating at least one feedback channel to a wirelessterminal in a MIMO-OFDM system. At step 1600, the base station transmitsto the wireless terminal, in a data frame, a unique identifier offeedback channel resources including at least one feedback channelassigned to the wireless terminal. At step 1610, the base stationtransmits a location of the feedback channel resources in the dataframe. At Step 1620, the base station transmits a total number of the atleast one feedback channels included in the feedback channel resourcesassociated with the unique identifier. As indicated at 1630 a loopingfunction is initiated for each of the at least one feedback channel ofthe feedback channel resources associated with the unique identifier. Atstep 1640, the base station also transmits to the wireless terminal afeedback type to be transmitted by the wireless terminal to the basestation. At step 1650, a feedback channel type to be transmitted by thewireless terminal to the base station. At step 1660, if the feedbacktype is a MIMO mode or permutation mode feedback type, the base stationalso transmits a feedback cycle for transmitting feedback informationpertaining to a transmission channel between the base station and thewireless terminal.

An illustrative example of an IE for allocating a feedback channelaccording to the method described above is shown below in Table 6. Thefeedback channel allocation IE has a field that identifies a uniqueindex value for the feedback resource assigned to a particular MSS, afield that indicates how often the feedback is to be repeated, a fieldthat indicates when the MSS is to start reporting feedback on a framelevel basis, a field that indicates how long the feedback channel is toremain allocated to the MSS, a field that indicates how many feedbackchannels are assigned to each index value, for each feedback channelwithin a frame a field that indicates the type of feedback that is to betransmitted on the feedback channel, a field that allocates the locationof that feedback channel for use by the MSS to transmit feedback, afield that indicates a CQICH type, and if the feedback type is a MIMOmode and permutation mode feedback type, a field that indicates afeedback cycle for transmission of MIMO mode and permutation modefeedback.

TABLE 6 CQICH Enhanced allocation IE format Size in Syntax bits NotesCQICH Enhanced Alloc IE( ) {  Extended-2 UIUC 4 CQICH Enhance Alloc IE() = 0x00 (Identifies type of IE)  Length 4 Length in bytes of followingfields  CQICH ID variable Index to uniquely identify the CQICH resourceassigned to the MSS  Period (=p) 2 A CQI feedback is transmitted on theCQICH every 2{circumflex over ( )}p frames  Frame offset 3 The MSSstarts reporting at the frame of which the number has the same 3 LSB asthe specified frame offset. If the current frame is specified, the MSSshould start reporting in 8 frames  Duration (=d) 3 A CQI feedback istransmitted on the CQI channels indexed by the CQICH ID for 10 ×2{circumflex over ( )}d frames. If d == 0b000, the CQICH isde-allocated. If d == 0b111, the MSS should report until the BS commandfor the MSS to stop.  CQICH Num 2 Number of CQICHs assigned to thisCQICH ID is (CQICH Num +1)  for (i=0; i < CQICH Num+1; i++) {   Feedbacktype 4 0b000-0b010 = Fast DL measurement/Default Feedback depending onCQICH types 0b011 = Quantized precoding weight feedback 0b100 = Index topreceding matrix in codebook 0b101 = Channel Matrix Information 0b111 =MIMO mode and permutation mode feedback 0b110 = Reserved   Allocation 6Index to the fast feedback index} channel region marked by UIUC = 0  CQICH Type 3 0b000 = 6-bit CQI, 0b001 = DIUC-CQI, 0b010 = 3-bit 0b011= 4-bit 0b100 = 5 0b101-0b111 = reserved A DIUC-CQI is a CQI channelthat uses a modulation and coding level derived from the DIUC.  if(Feedback type == 0b111) {   MIMO 00 = No MIMO and permutationpermutation feedback mode feedback cycle} 01 = the MIMO and permutationmode indication shall be transmitted on the CQICH indexed by the CQICHID every 4 frames. The first indication is sent on the 8th CQICH frame.10 = the MIMO mode and permutation mode indication shall be transmittedon the CQICH indexed by the CQICH_ID every 8 frames. The firstindication is sent on the 8th CQICH frame. 11 = the MIMO mode andpermutation mode indication shall be transmitted on the CQICH indexed bythe CQICH ID every 16 frames. The first indication is sent on the 16thCQICH frame.  Padding variable The padding bits are used to ensure theIE size is integer number of bytes. }

The “CQICH ID” field uniquely identifies a fast feedback channel onwhich a MSS can transmit fast feedback information. With thisallocation, a one-to-one relationship is established between the CQICHID and the MSS.

The “Feedback type” field specifies the types of the feedbackinformation on CQICH.

The “MIMO permutation feedback cycle” field specifies the MIMO andpermutation mode fast feedback cycle.

Table 7 provide a list of example encodings of payload bits for use intransmitting feedback information from the MSS to the BS. Some of theencoding values are 4 bits for use on the standard 4 bit fast feedbackchannel and some of the encoding values are 6 bits for use on theenhanced 6 bit fast feedback channel.

TABLE 7 Example encoding of payload bits for Fast-feedback slot ValueDescription 0b0000 STTD and PUSC/FUSC permutation 0b0001 STTD andadjacent-subcarrier permutation 0b0010 SM and PUSC/FUSC permutation0b0011 SM and adjacent-subcarrier permutation 0b0100 Hybrid andPUSC/FUSC permutation 0b0101 Hybrid and adjacent-subcarrier permutation101110-110110 Depending on if antenna grouping, antenna selection or areduced precoding matrix code book is used. 110111 Closed loop precodingwith 1 stream. 111000 Closed loop precoding with 2 streams. 111001Closed loop precoding with 3 streams. 111010 Closed, loop precoding with4 streams. 111011-111111 Reserved

In some situations of OFDM Closed-Loop (CL) MIMO communication betweenthe base station and the wireless terminal or MSS as described above,the terminal feeds back information to the base station that allows thebase station to provide the optimum signal to be received by theterminal. In some aspects of OFDM CL MIMO communication, a mathematicalprocessing method commonly known as Singular Value Decomposition (SVD)is used by the MSS to determine optimal conditions for transmission bythe BS to the MSS and feeds back this information to the BS to useappropriately in encoding the information to be transmitted by the BS.In some aspects of OFDM MIMO communication, the terminal can select asubset of BS antennas from a full group of BS antennas for transmissionof downlink information to the MSS based on-basic criteria measurable bythe terminal, for example channel power strength between the BS and MSS.These aspects are more fully described in International PatentApplication No. WO 2005/124044A1, which is assigned to the assignee ofthe present application, and is hereby incorporated by reference. Inboth of these above-mentioned aspects at least one feedback channel isused to allow the MSS to communicate desired information with the BS.

STTD/SM FFD Feedback Options

For STTD/SM mode communication with Frequency Division Duplexing (FDD)there are at least three MIMO modes for which feedback is used. For aDiversity Permutation mode the terminal transmits feedback related toSTTD/SM mode selection and Average CQI. For an AMC Band Permutation modethe terminal transmits feedback related to STTD/SM mode selection andCQI of top X band (layer index+band index+CQI). For an Antenna GroupingBased mode, for both diversity and AMC band permutation the MOStransmits feedback related to Group index and CQI. In some embodiments,feedback for the STTD/SM modes is provided by the feedback methodsdescribed above.

SVD FDD Feedback Options

When using SVD mode processing there are at least five modes for whichsome form of feedback is used. A first mode relates to Close loop andAMC band permutation. A second mode relates to H matrix that involvesdifferential encoding. A third mode relates to W vector that involvesdifferential encoding. A fourth mode relates to v and CQI of top Xlayers that involves differential encoding. A fifth mode relates to Codebook index of V and top X layers that involves differential encoding.Other modes are described in International Patent Application No WO2005/125044A1.

There are multiple embodiments for providing feedback from the MSS tothe BS for SVD modes. In one such embodiment, one or more dedicated fastfeedback channels are assigned, for example one or more CQICHs, toprovide MIMO channel feedback. In this embodiment an appropriate IE isused by the BS to send allocation information to the MSS identifyingwhen the MSS is to send feedback information.

With reference to FIG. 17, such a scenario will now be described. At afirst point in time, indicated at 1700 the BS sends an feedback resourceallocation IE that indicates a total number of feedback channels to beallocated over one or more frames to allow the MSS sufficient capacityto transmit feedback requested by the BS. The feedback resourceallocation IE also provides the MSS with an indication of the form ofthe feedback being requested by transmitting an indication of the howthe feedback is to be transmitted by the MSS. For example whether STTDor BLAST, the average CQI, the layer index and the H, W or V matrixdepending on the antenna configuration. At a subsequent point in time,indicated at 1710, the MSS transmits the requested feedback to the BSusing the selected number of feedback channels. Although notspecifically shown in FIG. 17, the MSS may transmit the feedbackinformation requested by the SS in multiple frames as described below,in which case there would be multiple instances of 1710.

In some embodiments, the BS allocates uplink resources depending on theurgency that the BS requires the feedback information from the wirelessdevice. If there is a high urgency, the BS may designate multiplefeedback channels in a single frame so as to obtain all the feedbackinformation as soon as possible. If there is a lower urgency, the BS maydesignate one or more feedback channels in multiple frames, eitherconsecutive frames or frames having a designated periodicity.

The feedback channels may be represented by fast feedback channels 222in FIG. 6. If more than one feedback channel is used, the MSS uses thefeedback channels as a single uplink resource to send the feedbackinformation to the BSS. For example if the feedback information requires15 bits and four 4 bit feedback channels are allocated in a singleframe, the MSS sends the 15 bits together in the single frame on the 16bits comprising the four feedback channels. If the feedback informationrequires IS bits and four 4 bit feedback channels are allocated in twoconsecutive frames, the MSS sends a first 8 bits of the 15 bits togetheron 8 bits comprising two feedback channels in the first frame and theremaining 7 bits of the 15 bits on the 8 bits comprising two feedbackchannels in the second frame. When the number of bits of feedbackinformation does not fill an integer number of allocated feedbackchannels, the remaining bits not required may or may not be used forsubsequent transmission of feedback information by the MSS.

The above-described situations are but examples of how feedback channelsmay be allocated in one or more frames. It is to be understood that anyreasonable number of feedback channels could be allocated in any numberof frames according to embodiments of the invention and still be withinthe scope of the invention.

An embodiment of the invention will now be described with respect toFIG. 18. FIG. 18 is a flow chart for a method of dynamically allocatingat least one feedback channel to a wireless terminal in a MIMO-OFDMsystem. At step 1800, the base station transmits to at least onewireless terminal an indication of a total number of feedback channelresource assignments, one per respective MSG as desired, for a dataframe. As indicated at 1810 a looping function is initiated for eachfeedback channel resource assignment of the total number of feedbackresource assignments. At step 1820 the base station transmits a uniqueidentifier associated with a respective wireless terminal for which thefeedback channel resource assignment is being assigned and at step 1830a location of the feedback channel resources in the data frame. At step1840, it is determined if the feedback channel is currently notde-allocated. If the feedback resource is currently not de-allocated,then at step 1850, the base station transmits a total number of feedbackchannels allocated to the respective wireless terminal associated withthe identifier, and at step 1860, a format index for indicating a typeof feedback information pertaining to a transmission channel between thebase station and the respective wireless terminal.

An example of a feedback channel IE is shown in Table 8. This IE is usedby the BS to assign one or more fast feedback channels to the MSS forthe MSS to provide MIMO feedback. The feedback channel allocation IE hasa field that identifies a number of feedback channel assignments orallocations to be made by the IE, a field that for each assignment setsan index value for the feedback channel assigned to the MSS, a fieldthat sets how long the feedback channel is to remain allocated to theMSS, a field that sets when the MSS is to start reporting feedback on aframe level basis, a field that sets how often the feedback is to berepeated, if the feedback channel is not allocated, a field that sets anumber of feedback channels allocated to the MSS identified by the MSSbasic CID, a field that sets the number of feedback values formattedbased on the “Format index” field that set the type of feedback is to betransmitted on the feedback channel, a field that sets the indication ofthe length of AMC band index, and a field that sets the indication ofthe length of CQI value index and sets the format index. The formatindex is an indication of a particular format to be used in transmittingfeedback information from the MSS to the BS.

TABLE 8 MIMO CQICH Alloc IE Size in Syntax bits Notes MIMO CQICH AllocIE ( ) {  Extended UIUC 4 Identifies type of IE  Length 4 Length inbytes of following fields  Num Assignments 5 Number of assignments inthis IE  For (i=0; i < Num Assignments; i++) {   CID 16 MSS basic CID  Duration(d) 3 The CQICH is assigned to a MSS for 10x2^(d) frames; If d= 0b000, the CQICH is deallocated; If d = 0b111, the MSS shall reportfeedback information using the assigned resource until the BS commandsfor the MSS to stop   Frame offset 3 The MSS starts to provide MIMOfeedback at the frame number which has the same 3LSB as the specifiedframe offset. If the current frame is specified, the MSS shall starttransmit feedback in 8 frames.   If (d !=0b000) {    Num CQICH 4 Numberof CQICHs allocated to Allocation the MSS identified by the MSS basicCID    Num MIMO 3 Number of feedback values feedback formatted based onthe “Format index” field defined below    Length of band 3 Indication ofthe length of AMC index band index    Length of CQI 2 Indication of thelength of CQI value index value index 0b00: 4 bits 0b01: 5 bits 0b10: 6bits 0b11: reserved    Format Index 3 See Table 9 below   }  } }

Table 9 includes a list of example feedback formats that could be usedin the “Format Index” field of Table 8.

TABLE 9 MIMO feedback formats Format index Feedback contents 1.(STTD/BLAST STTD/BLAST selection (1 bit) + Average diversitypermutation) CQI (the number of bits = length of CQI value indexindicated in the corresponding MIMO CQICH Alloc IE, e.g., 4/5/6 bits) 2.STTD/BLAST antenna STTD/BLAST selection (1 bit) + Antenna permutationgroup index (2 bits) + average CQI (the number of bits = length of CQIvalue index indicated in the corresponding MIMO CQICH Alloc IE, e.g.,4/5/6 bits) 3. STTD/BLAST for AMC Layer index (2 bits) + AMC band indexband permutation (number of bits = Length of band index indicated in thecorresponding MIMO CQICH Alloc IE) + CQI (the number of bits = length ofCQI value index indicated in the corresponding MIMO CQICH Alloc IE,e.g., 4/5/6 bits) 4. Feedback Channel H Layer index (2 bits) + H (xxbits- for AMC band depending on antenna configuration) permutation) 5.Feedback Layer index (2 bits) + W (xx bits- transmission weightsdepending on antenna configuration + CQI for AMC band (the number ofbits = length of CQI permutation value index indicated in thecorresponding MIMO CQICH Alloc IE, e.g.. 4/5/6 bits) 6. Feedback Vmatrix Layer index (2 bits) + V (xx bits- for AMC band and depending onantenna configuration) + CQI permutation (the number of bits = length ofCQI value index indicated in the corresponding MIMO CQICH Alloc IE,e.g., 4/5/6 bits)

The number of bits in the “feedback contents” column of Table 9 areexamples for each associated “Format Index” and it is to be understoodchat the number of bits to represent the “Feedback contents” may be moreor less than those shown in Table 9. More generally, other types offeedback type and feedback content that are consistent with theintention of the invention as described herein, but not specificallyincluded are to be considered within the scope of the present invention.

After the MSS receives such an IE, the MSS may continuously transmit theinformation defined in Table 8 during the assignment duration or untilthe feedback channels are deallocated. In some embodiments, theinformation bits are mapped to the assigned feedback channels in thefollowing manner. For the first frame where feedback channels isallocated, the payload of the first CQICH is first filled and thepayload of second feedback channel is then filled. This continues untilall assigned feedback channels in the frame are filled up. This processis repeated for each subsequent frame.

Table 10 illustrates an example of a format used at 1710 in FIG. 17 bythe MSS to transmit the feedback information to the MS after receivingthe contents of the “MIMO CQICH Alloc” IE.

TABLE 10 MIMO feedback Size in Syntax bits Notes for (i=0; i < Num MIMOIf the Num MIMO feedback; i++) feedback > 1, the feedback, either layerbased or AMC band based, shall be in the order so that the layer or AMCband who has the maximum CQI appears first. {  Feedback contentformatted 3 See “Feedback Content” as indicated by format index in Table9. } If (Format index == 4)  Average interference 4 Average interferenceIf (Format index == 3)  STTD/BLAST Selection 1 0b0 : STTD is selected0b1 :BLAST is selected

Another embodiment for providing feedback from the MSS to the BS for SVDmodes will now be further described with respect to FIG. 19. At a pointin time, indicated at 1900, the BS polls the MSS for desired feedbackwith a feedback request message. At 1910, in response to the feedbackrequest message the MSS transmits a feedback response message containingthe feedback information requested by the BS.

Table 11 illustrates an example of a structure for a “MIMO FeedbackRequest” message. This message may be used by the BS to request MIMOfeedback information from the MSS that supports MIMO operation.

TABLE 11 MIMO Feedback Request message format Size in Syntax bits NotesMIMO Feedback Request message format ( ) {   Num MIMO feedback 3 Numberof feedback values formatted based on the Format index defined below  Length of band index 3 Indication of the length of AMC band index  Length of CQI value 3 Indication of the length of index CQI valueindex   Format Index 3 See Table 9 }

Table 11 is an example of fields that may be included in the feedbackrequest message. The fields in the feedback request message are includedto reflect the feedback information requested by the BS. It is to beunderstood that additional fields or fewer fields associated with thefeedback process may be used in requesting feedback informationdepending on the type of feedback that is being requested.

Table 12 illustrates an example of a structure for a “MIMO FeedbackResponse” message. This message may be used by the MSS to supply MIMOfeedback information to the BS as a reply after receiving a “MIMOFeedback Request” message or as an unsolicited MIMO feedback message.

TABLE 12 MIMO Feedback Response message format Size in Syntax bits NotesMIMO Feedback Response message format ( ) {   Num MIMO feedback 3 Numberof feedback values formatted based on the Format index defined below  Format index 3   for ( i=0: i < Num MIMO If the Num MIMO feedback:i++) feedback > 1, the feedback, either layer based or AMC band based,shall be in the order so that the layer or AMC band who has the maximumCOJ appears first.   { Feedback content formatted as 3 See “Feedbackindicated by format index Content” in Table 9. If (Format index == 4)Average interference 4 Average interference If (Format index == 3)STTD/BLAST selection 1 0b0: STTD selected 0b1: BLAST selected }

Table 12 is an example of fields that may be included in the feedbackresponse message. The fields in the feedback response message areincluded to reflect the feedback information transmitted by the MSS. Itis to be understood that additional fields or fewer fields associatedwith the feedback process may be used in providing feedback informationdepending on the type of feedback that is requested.

A further embodiment for providing feedback from the MSS to the BS forSVD modes is an autonomous MIMO feedback message sent by the MSS. Inthis case the MSS, without being solicited for a response, sends amessage to the BS containing feedback information. The message sent bythe MSS may be similar in structure to the “MIMO Feedback Response”message format.

The examples of the format for the “MIMO feedback” used in response tothe “MIMO CQICH allocation” IE and the request and response messagesdescribed above in Tables 10, 11 and 12 are but a single example of eachformat. It is to be understood that the “MIMO feedback” format and therequest and response messages may contain additional of fewer fields forrequesting or reporting feedback, and are still within the scope of thepresent invention if used for requesting or reporting feedback betweenthe MSS and the BS

Yet another embodiment for providing feedback from the MSS to the BS forSVD modes is by using a MAC feedback header using methods similar tothose described above in FIGS. 7 and 10.

The feedback headers of FIG. 11 or 12 are examples of a feedback headerthat may be used by the MSS to provide, closed-loop MIMO feedbackinformation. One or more feedback headers may be sent by the MSS at onceif one header is not enough to contain all the feedback information tobe sent by the MSS.

The “Feedback Type” field is set to indicate the type of feedback. Inthe feedback header, without the use of the “Basic CID field” there are32 bits of payload for the purpose of MIMO feedback.

The mapping of feedback information bits onto the Feedback header isprovided by filling the payload field in the first MIMO feedback headerand then the second, until preferably all the information bits aremapped.

STTD/SM TDD Feedback Options

For time division duplex (TDD) MIMO channel feedback, STTD/SM modeinformation can be handled in a similar manner that that of the as theSTTD/SM FDD case above.

SVD TDD Feedback Options

For TDD MIMO channel feedback, SVD mode information can be handled byany one of several different embodiments. A first embodiment involvesassigning one or more dedicated fast feedback channels to provide MIMOchannel feedback in a similar manner to the SVD method for FDD.

In a second embodiment no explicit H or W or V is fed back to the BS. Afast feedback channel is designed go that the sub-carriers (48sub-carriers) are distributed across a whole band in one or more OFDMsymbol. At the MSS side, the MSS transmits a CQI payload. At the BSside, the DS can decode COT payload and at the same time, derives thechannel information from the UL received CQI signal using a appropriatealgorithm.

In a third embodiment, no explicit R or W or V is fed back to the BS. Afast feedback channel is designed so that preferably the sub-carriers(48 sub-carriers) are distributed across a whole band in one OFDMsymbol. The MSS transmits the CQI payload and a predetermined pilotpattern in a TDM fashion. When the MSS sends CQI, the CQI payload istransmitted. When the MSS transmits a pilot, the pilot is directlymapped to the 48 sub-carriers, The BS derives required channelinformation from the UL pilot.

Numerous modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein.

The invention claimed is:
 1. A method in a base station for enablingfeedback in an uplink transmission of a communication system from awireless terminal to a base station, the method comprising: the basestation transmitting an indication of a type of feedback informationrequested by the base station, the indication comprising an informationelement in an uplink resource allocation portion of a data frame, thebase station transmitting an indication of a type of feedbackinformation requested by the base comprising: the base stationtransmitting: a) a total number of feedback resource allocations for adata frame; b) an indication if feedback resources are to be dedicated;c) for each feedback resource allocation of the total number of feedbackresource allocations, the base station transmitting: i) an identifierfor the wireless terminal for which the feedback resource allocation isoccurring; ii) when the feedback resource is currently not released, thebase station transmitting:  an indication of feedback type requested bythe base station and a location of a subsequent data frame withreference to the data frame indicating when feedback informationrequested by the base station will be received on an allocated feedbackresource;  when feedback resources are to be dedicated as a part of thismethod as indicated above, allocating a feedback resource bytransmitting location information for the feedback resource.
 2. Themethod of claim 1, wherein the information element comprises a feedbackpolling information element.
 3. A method for dynamically allocating atleast one feedback channel to a wireless terminal in a Multiple-Inputand Multiple-Output Orthogonal Frequency Division Multiplexing(MIMO-OFDM) system, the method comprising: a base station transmittingto the wireless terminal in a data frame: 1) a unique identifier offeedback channel resources including at least one feedback channelassigned to the wireless terminal; 2) a location of the feedback channelresources in the data frame; 3) a total number of the at least onefeedback channels included in the feedback channel resources associatedwith the unique identifier; 4) for each of the at least one feedbackchannel of the feedback channel resources associated with the uniqueidentifier, the base station transmitting to the wireless terminal: i) afeedback type to be transmitted by the wireless terminal to the basestation; ii) a feedback channel type to be transmitted by the wirelessterminal to the base station; iii) when the feedback type is a MIMO modeor permutation mode feedback type, a feedback cycle for transmittingfeedback information pertaining to a transmission channel between thebase station and the wireless terminal.
 4. The method of claim 3,wherein the base station transmitting comprises transmitting the uniqueidentifier, the location, the feedback type, and the respective feedbackcycles in a format of a channel allocation information element.
 5. Amethod in a base station for enabling feedback in an uplink transmissionof a closed-loop communication system from at least one wirelessterminal to a base station, the method comprising: transmitting arequest for feedback information and an allocation of uplink resourcescomprising at least one feedback channel in one or more data frames onwhich the at least one wireless terminal is to transmit the requestedfeedback information to the base station; receiving the feedbackinformation in accordance with the request on the at least one allocatedfeedback channel in the one or more data frames, until all the requestedfeedback information is received by the base station, the allocation ofuplink resources on which the at least one wireless terminal is totransmit the requested feedback information comprising dynamicallyallocating at least one feedback channel to the at least one wirelessterminal in a MIMO-OFDM system, comprising: a base station transmittingto the at least one wireless terminal: a) an indication of a totalnumber of feedback channel resource assignments for the one or more dataframes; b) for each feedback channel resource assignment of the totalnumber of feedback resource assignments, the base station transmitting:i) an identifier for a respective wireless terminal for which thefeedback channel resource assignment is being assigned; ii) a locationof the feedback channel resources in the one or more data frames; iii)when a feedback channel is currently not de-allocated, the base stationtransmitting:  a total number of feedback channels allocated to therespective wireless terminal associated with the identifier;  a formatindex for indicating a type of feedback information pertaining to atransmission channel between the base station and the respectivewireless terminal.
 6. The method of claim 5, wherein the base stationtransmitting comprises transmitting the indication of the total numberof feedback channel resource assignments, the identifier, the location,the total number of feedback channels, and the format index in a formatof a channel allocation information element.